How Many Neon Tetras in a 5 Gallon Tank? 10 Gallon? 20 Gallon?

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Tetras are a popular fish for those who love keeping an aquarium and enjoy watching the small housed inside. Since tetras are common and easy to care for, it is no wonder that you are bound to want a few for your aquarium. Neon tetras are but one type of tetra available. There are also cardinal tetras, rosy tetras, ember, green neon, and even diamond variations! Recently, glofish tetra and lemon tetra have also been introduced, so you can have a shimmering school of tetra fish in your tank.

Since neon tetras (and their other vibrantly colored brethren) are small in comparison to other fish, you might be thinking that you can add them to a 5 gallon tank with no problems. We will get into calculating how many fish per gallon of water later on as well as provide an answer to how many tetras in a 5 gallon tank.

About Tetras and Care Tips to Consider


Care Level:Easy
Color Form:Blue, Red, Translucent
Lifespan:8 Years
Minimum Tank Size:5 Gallons
Tank Set-Up:Freshwater: Planted

Let’s first acquaint ourselves with the humble tetra fish. This will help you create the most comfortable environment for your fish and ensure they stay healthy and energetic for their lifespan. Tetras are freshwater fish native to Central America, South America, and Africa. They are also omnivorous, so they will feed on flakes, brine shrimp, blood worms, and even plant life.

Neon tetras are very active and enjoy swimming around their home, hiding in and darting out of plants, wood, and other decorations. This means that the more room they have, the happier they will be. But you can’t have just one or two in a tiny bowl or even a huge tank.

Neon tetra are known as shoaling, or schooling, fishes. These are fishes that tend to live in groups for safety and other social reasons. Tetras, for instance, need to be in schools, because, even though they are peaceful, they can get scared and agitated if their numbers are too few. For this reason, you should always make sure you have room for at least 5-6 tetra fish in a tank or bowl.

In the wild, a single school of tetras will consist of hundreds, sometimes thousands of fish. Imagine how cool that looks! Of course, you can’t have a hundred tetras in an aquarium. If you want a school, though, you will need about 10-15 neon tetras.

Keep this in mind when we get into how many tetras in a 5, 10, or 20 gallon tank.

Another factor to think about is the pH level of the fish tank. Tetras adapt well, but they are happiest at a pH range of 6-7. If the pH level is above 7.5, they may become stressed and ill.

Source: Petful

You will know when your tetras, regardless if they are glofish tetras, neon tetras, or another kind, are stressed when their bright opalescent scales start to lose their color, and the fish lose their vigor. This can happen when your fish are either overcrowded or there is too few for them to feel safe.

Do Neon Tetras Need An Air Pump?

No. Generally speaking, you do not need an air pump for neon tetras. As long as you have enough room for your fish in an adequately sized tank, there will be more than enough oxygen in the water for them to live comfortably. Additionally, you can add aquarium plants, like red root floaters, to help produce more oxygen.

How Many Tetras in a 5 Gallon Tank?

4-5 Neon Tetra

First, you need to calculate how many gallons a single tetra needs to be happy. For small fish, you need about 1 gallon of water for a fish that grows to about 1.5-2.0 inches (3.8-5.0 cm). Since tetras grow to about 1.5-1.75in long, you need about 1-2 gallons per fish. This is why it is important to understand that neon tetras can only be happy in a school.

Tips For Keeping Tetras in a 5 Gallon Tank

For those who are beginners, it may seem weird that 5 gallon tanks are said to be harder to maintain than larger tanks by more experienced aquarium owners. The reason is this: you need to construct a more careful balance. There is less room for mistakes.

Still, if you want to give small tanks a go or have had success with a 5 gallon tank in the past, then you could possibly have 4-5 tetras in your 5 gallon tank by considering the following;

  • You can’t overfeed your fish
  • You will need plenty of live plants to help with oxygen
  • You will require a water heater and filter
  • Small tanks need more frequent maintenance
  • Water changes must be done weekly
  • Keep tabs on the water parameters, since things can go wrong quickly

Can Neon Tetras Survive in a 5 Gallon Tank

So, let’s review for a second. A 5 gallon tank is not the best option for keeping neon tetras, but that doesn’t mean it cannot be done. You should provide your fish with plenty of horizontal space for swimming and have rocks and plantlife for them.

Therefore, those who are less experienced with keeping fish should consider a 10 gallon tank or above for keeping tetras and other sorts of small fish.

How Many Tetras in a 10 Gallon Tank?

6-7 Neon Tetra

Going back to our formula, remember that a 1.75in long neon tetra will need about 1.75 gallons of water. Considering this, a 10 gallon tank could fit around 6-7 neon tetras without any fuss. But, this is an estimate. You don’t know how long your neon tetras are going to grow, and if you plan on adding other tank mates, such as a betta fish or danios or zebrafish, you will have less space for your neon tetras.

To give your fish plenty of room to swim around, you might only put 5-6 tetras in a 10 gallon tank. Wait, you think, isn’t that around the same amount as the 5 gallon tank?

It is! This is why 10 gallons is considered the best solution for a small group of tetras, not 5 gallons. Of course, you could bump up the number to 6-8 tetras to a tank if they are smaller, but then you have to follow the same guidelines for a cramped 5 gallon tank.

How Many Tetras in a 20 Gallon Tank?

10-12 Neon Tetra

Here we have 20 gallons divided by 1.75 inches, giving us 11.4, or 10-12 fish. At last, we have reached the tank size that would allow for an actual school of tetra fish! A 20 gallon tank is perfect for a couple of reasons.

First, you will not overcrowd or stress out your tetras. Furthermore, your fish will have plenty of room to swim horizontally and with their school. While 10 gallon tanks can provide this for a smaller school of 5-6 fish, they will feel less secure than if they had about 20 gallons to swim around.

In short, if you are planning on keeping a large group of tetras and budget allows, you should opt for a 20 gallon aquarium.

Can I Keep Other Fish With My Tetras?

The basic answer is yes; but there’s more to it than compatibility. A popular pairing for tetras are betta fish, since they are both colorful, and if plenty of room is provided, will get along fairly well.

However, you cannot expect to cram tetras and tank mates into a 5 gallon tank. Larger fish, like bettas, catfish, snails, and algae eaters, all need space too. A betta needs at least 3 gallons of water to itself, with the ideal amount being 5-10 gallons. That’s for a single fish.

The more tetras you have in a 10 gallon or 20 gallon tank, the less tank mates. For example, if you wanted to split a 10 gallon tank among tetras and guppies, that would be enough space for 5 fish. In other words, 5 guppies or 5 neon tetras. Alternatively, 2 guppies and 3 tetras and vice versa.


How many tetras in a 5 gallon tank, you ask? About 4-5 fish, if you are going to be extremely careful. Of course, in terms of having happier, healthier fish, you should always consider giving them more room and plenty of plants, rocks, and clean water. Opt for at least 10 gallons to keep neon tetras, and go bigger if you want more than one type of fish.

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